Access to a patient's vascular system may be established by a variety of temporary or permanently implanted devices. For example, temporary access to a patient's vascular system may be accomplished by the direct percutaneous introduction of a needle into the patient's blood vessel. While such a temporary and direct approach may be relatively simple and suitable for applications that are limited in frequency or duration, such as intravenous feeding and/or intravenous drug delivery, this temporary approach may not be suitable for procedures that are frequently repeated or that require vascular access for relatively long time periods of time, such as hemodialysis or other similar extracorporeal procedures.
Accordingly, a variety of implantable devices have been proposed to provide a convenient method for repeatedly introducing fluids, such as medicaments, into the vasculature of a patient. Typically, such implantable device comprise a housing that encloses an internal fluid chamber or cavity. An access aperture defined through the housing and sealed by a penetrable septum provides access to the internal fluid chamber, which is typically in fluid communication with an implanted catheter attached to a patient's vasculature.
Quantities of fluid, such as medication, blood, or the like, may be introduced into, or withdrawn from, a patient's vasculature using conventional implantable device by: 1) penetrating the septum of the implanted device using a percutaneously inserted needle; 2) positioning at least the tip of the needle within the internal fluid reservoir or cavity enclosed in the device housing; and 3) discharging fluids through the needle into the internal fluid cavity. The discharged fluids may then be directed through the distal end of the implanted catheter connected to the implanted device to an entry point into the venous system of the body of the patient. Blood may also be aspirated through the implanted device in a similar manner.